1. Field of the Invention
The present invention relates to a video signal recording apparatus, and, more particularly, to a video signal recording apparatus suitable for recording a still picture.
2. Description of the Related Art
Heretofore, in this type of recording and reproducing apparatus there has been no combined-use apparatus which is capable of recording by distinguishing a motion picture and a still picture. However, if we dare to cite such an apparatus, a presently available one is merely such that a still picture is reproduced simply in the so-called reproduction pause mode or the like as one frame in a motion picture by using a magnetic recording and reproducing apparatus (VTR) for motion picture use which uses a magnetic tape as a recording medium. However, the quality of the still picture is in most cases inferior to that of the motion picture.
On the other hand, a recording apparatus exclusively used for the still picture has been conceived. In this case, however, if, for instance, an attempt is made to record one field of a television signal with high fidelity on a real-time basis as a digital signal, for example, a super-high speed digital processing circuit and the like are required, so that the apparatus becomes large. In addition, when recording is effected as an analog signal, it is impossible to expect for a substantial improvement in the quality of the picture.
With reference to FIG. 1, description will be made of reproduction of the still picture in a conventional so-called 8 mm VTR which employs a 8 mm-wide magnetic tape.
In FIG. 1, reference numeral 1 denotes a magnetic tape (hereafter referred to as the "tape"); 102, a pinch roller; 103, a capstan motor; 104, a rotary drum; 106, a frequency signal (drum FG) generator concerning the rotational speed of the drum 104; 105, a pulse (PG) generator concerning the rotary phase of the drum 104; 107, 108, 112, 114, 115, and 119, amplifiers, respectively; 109, a drum phase control circuit; 110, a drum speed control circuit; 111, 118, adders, respectively; 116, a tracking error (ATF) signal generator; 113, a frequency signal (capstan FG) generator relating to the rotational speed of the capstan motor 103; 117, a capstan speed control circuit; and 120, 121, magnetic heads (hereafter referred to as the "head"), respectively.
In FIG. 1, a phase error signal from the phase control circuit 109 and a speed error signal from the speed control circuit 110 on the basis of a drum PG and a drum FG are added by the adder 111, and the rotary drum 104 is driven by this added signal. Consequently, the rotation of the drum 104 is controlled such as to compensate for their errors.
Meanwhile, the capstan motor 103 effects tracking control using a speed error signal supplied from the speed control circuit 117 obtained on the basis of the capstan FG as well as an ATF (automatic tracking finding) signal supplied from the ATF signal generator 116 using a known 4-cycle pilot system.
In the state of reproduction of the still picture, control is effected by means of the circuit shown in FIG. 1 in such a manner that the head traces the magnetic tape as in the case of (i) or (ii) of FIG. 2.
FIG. 2 is a diagram illustrating the condition of tape tracing by the heads during (i) the so-called frame still reproduction and (ii) the so-called field still reproduction. Description will be made hereafter with reference to FIG. 2.
In FIG. 2:
(i) In the frame still reproduction, two fields are reproduced alternately, and, using two heads A, B, only the tracks whose azimuth coincides with those of the heads A, B are reproduced alternately. For this reason, a reproduction area per field in both cases becomes approximately one half less than in the case of normal reproduction, as shown in the drawing, with the result that the signal-to-noise ratio drops. In addition, since the video signals of these two fields have a time difference of 1/60, there is a possibility of the still picture becoming blurred in a scene in which the movement is fast. PA1 (ii) In the field still reproduction, only one field of the video signals constituting one frame out of two fields is reproduced repeatedly by means of heads exclusively used for the still picture (i.e., two heads having a 180.degree. phase difference and an identical azimuth). Consequently, blurring as found in the frame still reproduction does not occur. However, in comparison with normal reproduction, a drop in the signal-to-noise ratio, and a deterioration in the vertical resolution are basically unavoidable.
In terms of human visual characteristics, high picture quality is generally required for the still picture compared with the motion picture. Furthermore, in the case of the still picture, since it is conceivable that the picture may be printed out and viewed in a fixed form on a sheet, higher picture quality is required. However, the still picture using a conventional VTR has a drawback in that the picture quality becomes aggravated in comparison with the motion picture for the aforementioned reasons.
Furthermore, as described above, it has been difficult to obtain high-quality pictures even in recording apparatus exclusively used for the still picture.